Three Mile Island was the most serious accident ever to happen in nuclear power plant history in the United States. The accident happened at approximately 4 a.m. on Wednesday, March 28th, 1979. It occurred in the town of Middletown, Pennsylvania.
A mechanical or electrical failure prevented the main feed water pumps from sending water to the steam generators that remove heat from the reactor core. This caused the plant's turbine-generator and then the reactor itself to automatically shut down. Immediately, the pressure in the primary system (the nuclear portion of the plant) began to increase. In order to control that pressure, the relief valve opened. The valve should have closed when the pressure fell to proper levels, but it didn't because it was stuck open to the top. Instruments in the control room, however, indicated to the staff that the valve was closed. So the staff was unaware that cooling water was rushing through the stuck open valve.
This is an animated diagram on how the accident at Three Mile Island occurred, notice howthe water is pouring into the stuck open valve, causing the accident to happen in the first place.
When Three Mile Island first occurred, some weren't sure on whether they should evacuate or not. Some were being told to pack up and leave by others, while others were told it was entirely under control. The evacuation plans that the governor had created were thoughtless and everybody would have been racing to the same bridges and exits. The governor didn't want to cause panic among Pennsylvania, but by Friday, March 30, he advised pregnant women and school-age children to leave the area. After this, many of the Pennsylvania citizens packed up their belongings and left. More than 140,000 fled the area.
These are the evacuation routes taken during Three Mile Island. This is as far as they had to evacuate during the incident.
Radioactive gases from the reactor cooling system built up in the makeup tank in the auxiliary building. The compressors leaked, and radioactive gas was leaked into the environment, but not enough to actually do anything to the environment. Although the nuclear explosion in Chernobyl caused many drastic health and environmental effects, this nuclear explosion was on a much smaller scale.Everybody that had been in the midst of Three Mile Island, in the area surrounding the plant, was beyond concerned that there was a threat of cancer. Because of those concerns, the Pennsylvania Department of Health for 18 years maintained a registry of more than 30,000 people who lived within five miles of Three Mile Island at the time of the accident. The state's registry was stopped in mid 1997, when no evidence whatsoever was found that cancer or any other radiation-caused disease occurred. More than a dozen independent studies were dedicated to discovering the threat of cancer, but nothing was discovered. The only after effect of this explosion was overwhelming stress and common nightmares.
The studies found that the radiation releases during the accident were minimal, well below any levels that have been associated with health effects from radiation exposure. The average radiation dose to people living within 10 miles of the plant was 0.08 millisieverts. The level of 0.08 mSv almost the same radiation as an X-ray, and would most certainly not harm anybody, no matter how close they were living to the power plant. But all in all, Three Mile Island showed that nuclear power plants were extremely serious and required much more important care.
Three Mile Island was the most serious accident ever to happen in nuclear power plant history in the United States. The accident happened at approximately 4 a.m. on Wednesday, March 28th, 1979. It occurred in the town of Middletown, Pennsylvania.
A mechanical or electrical failure prevented the main feed water pumps from sending water to the steam generators that remove heat from the reactor core. This caused the plant's turbine-generator and then the reactor itself to automatically shut down. Immediately, the pressure in the primary system (the nuclear portion of the plant) began to increase. In order to control that pressure, the relief valve opened. The valve should have closed when the pressure fell to proper levels, but it didn't because it was stuck open to the top. Instruments in the control room, however, indicated to the staff that the valve was closed. So the staff was unaware that cooling water was rushing through the stuck open valve.
When Three Mile Island first occurred, some weren't sure on whether they should evacuate or not. Some were being told to pack up and leave by others, while others were told it was entirely under control. The evacuation plans that the governor had created were thoughtless and everybody would have been racing to the same bridges and exits. The governor didn't want to cause panic among Pennsylvania, but by Friday, March 30, he advised pregnant women and school-age children to leave the area. After this, many of the Pennsylvania citizens packed up their belongings and left. More than 140,000 fled the area.
This is as far as they had to evacuate during the incident.
Radioactive gases from the reactor cooling system built up in the makeup tank in the auxiliary building. The compressors leaked, and radioactive gas was leaked into the environment, but not enough to actually do anything to the environment. Although the nuclear explosion in Chernobyl caused many drastic health and environmental effects, this nuclear explosion was on a much smaller scale. Everybody that had been in the midst of Three Mile Island, in the area surrounding the plant, was beyond concerned that there was a threat of cancer. Because of those concerns, the Pennsylvania Department of Health for 18 years maintained a registry of more than 30,000 people who lived within five miles of Three Mile Island at the time of the accident. The state's registry was stopped in mid 1997, when no evidence whatsoever was found that cancer or any other radiation-caused disease occurred.
More than a dozen independent studies were dedicated to discovering the threat of cancer, but nothing was discovered. The only after effect of this explosion was overwhelming stress and common nightmares.
The studies found that the radiation releases during the accident were minimal, well below any levels that have been associated with health effects from radiation exposure. The average radiation dose to people living within 10 miles of the plant was 0.08 millisieverts. The level of 0.08 mSv almost the same radiation as an X-ray, and would most certainly not harm anybody, no matter how close they were living to the power plant. But all in all, Three Mile Island showed that nuclear power plants were extremely serious and required much more important care.
Works Cited:
http://www.pbs.org/wgbh/amex/three/filmmore/description.html
http://www.world-nuclear.org/info/Safety-and-Security/Safety-of-Plants/Three-Mile-Island-accident/